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Yin Liu

Publications and source records attributed to Yin Liu.

At least 55 records · Page 3Linked to original sources
PubMed2005

Inhibitory effect of agmatine on proliferation of tumor cells by modulation of polyamine metabolism.

AIM: To assess the inhibitory effect of agmatine on tumor growth in vivo and tumor cell proliferation in vitro. METHODS: The transplanted animal model, [3H]thymidine incorporation assay,3-[4,5-dimethythiazol-2-yl]-2,5-diphenyltetrazolium assay, and lactate dehydrogenase (LDH) release assay were performed. RESULTS: Agmatine, at doses of 5-40 mg/kg, suppressed the S180 sarcoma tumor growth dose-dependently in mice in vivo and the highest inhibitory ratio reached 31.3% in Kunming mice and 50.0% in Balb/c mice, respectively. Similar results were obtained in the transplanted B16 melanoma tumor model. Agmatine (1-1000 micromol/L) was able to attenuate the proliferation of cultured MCF-7 human breast cancer cells in vitro in a concentration-dependent manner and the highest inhibitory ratio reached 50.3% in the [3H]thymidine incorporation assay. Additionally, in the LDH release assay, spermine (20 micromol/L) and spermidine (20 micromol/L) increased the LDH release significantly, but agmatine (1-1000 micromol/L) did not, indicating that the inhibitory effect of agmatine on the proliferation of MCF was not related to cellular toxicity. In the [3H]thymidine incorporation assay, putrescine (12.5-100.0 micromol/L) could reverse the inhibitory effect of agmatine on the proliferation of MCF concentration-dependently, suggesting that the inhibitory effect of agmatine on the proliferation of MCF might be associated with a decreased level of the intracellular polyamines pool. CONCLUSION: Agmatine had significant inhibitory effect on transplanted tumor growth in vivo and proliferation of tumor cells in vitro, and the mechanism might be a result of inducing decrease of intracellular polyamine contents.

Agmatine↗
PubMed2005

[A new precipitation distribution hydrological model and its application].

In distribution hydrological models, precipitation is the key input data for analyzing and computing hydrological processes. Finding a way to produce distribution precipitation data is a hotspot in hydrological research. This paper presented the hypothesis that the distribution of precipitation on the earth surface is the result of the effects of atmosphere system and terrain. Moreover, the spatial distribution of natural precipitation is a group of concentric ovals on the flat earth surface, and has a definite centre with maximum precipitation not affected by terrain. Supporting by the hypothesis, this paper established a new precipitation distribution hydrological model which could simulate the spatial distribution of precipitation, and modified the terrain effect on precipitation through Newton interpolation. The position of the precipitation centre and its precipitation amount were simulated in first time, and thus, the model could have a practical value in basin storm analysis and real-time runoff forecasting. The model was tested by the precipitation data of the Xichuan river basin in the Loess Plateau, which indicated that the model had a high precision.

Chemical Precipitation↗
PubMed2005

[Cultivation of ANAMMOX bacteria and the ammonium anaerobic oxidation technology in the plug flow bio-reactor].

It is feasible that the ANAMMOX bacteria can be enriched and cultivated to red granular in plug flow immobilized floc bioreactor. Average ammonium and nitrite removal rate are more than 98 %, and average total nitrogen removal rate is 86% combined with 14% nitrate production; the removal volumetric total nitrogen load is 2.56kg/(m3 x d). The influence of the influent substrate ratio of ammonium to nitrite on reactor's performance has been studied. The granule structure has been observed by the scan electro-microscope.

Bacteria, Anaerobic↗
PubMed2005

[Differential gene expression in nasopharyngeal carcinoma cell with reduced and normal expression of 6A8 alpha-mannosidase].

OBJECTIVE: To detect the differential display of mRNA expression between human nasopharyngeal carcinoma cell CNE-2L2 with reduced malignancy caused by transduction of a DNA antisense to 6A8 alpha-mannosidase cDNA (AS cell) and the wild type cell (W cell). METHODS: Differential display of mRNA expression was analyzed using DNA microarray analysis. The datasets were confirmed by Northern blotting and RT-PCR. RESULTS: Out of the 1069 genes analyzed, 34 genes were up-regulated in AS cells relative to W cells. Conversely, 42 genes were down-regulated. The genes, up-regulation of which might have suppressive effect on tumor malignant behaviors, were P130 mRNA for 130K protein, TGF-betaIIR alpha, GABBR1, TGFBR1, TNFAIP1, STANIN, E-CADHERIN, CTNNA1 and 2, RFX2, TMPO, etc. The genes, down-regulation of which might have suppressive effect on tumor malignant behaviors, were CD44, NDRG1, TGFB1, RPS5, LEGUMAIIN, CBS, CD59, SNRPA1, etc. The microarray datasets were confirmed by Northern blot and RT-PCR analysis. CONCLUSIONS: In comparison to the W cell, AS cell has up-regulation of 34 genes and down-regulation of 42 genes. Changes of the gene expression may play a role in the malignancy reduction of AS cell.

Gene Expression Profiling↗
PubMed2005

The efficacy and safety of adapalene gel 0.3% in the treatment of acne vulgaris: A randomized, multicenter, investigator-blinded, controlled comparison study versus adapalene gel 0.1% and vehicle.

A randomized, multicenter, investigator-blinded, active- and vehicle-controlled study was conducted to evaluate the efficacy and safety of adapalene gel 0.3% versus adapalene gel 0.1% and the corresponding gel vehicle. Subjects were assigned randomly to receive either adapalene gel 0.3%, adapalene gel 0.1%, or vehicle once daily for 12 weeks. A total of 214 subjects with moderate to moderately severe acne vulgaris were enrolled, and 85% of subjects completed the study. Adapalene gel 0.3% was significantly superior to adapalene gel 0.1% in total and noninflammatory lesion counts and in global severity score (P < .05 for all). A concentration-dependent increase in clinical benefit for all efficacy assessments was observed. As expected, there were also statistically significant differences in all efficacy parameters in the adapalene gel 0.3% group relative to the vehicle group (P < .001 for all). Treatment-related adverse events were mostly mild-to-moderate and similar between active groups. The results of this study show that adapalene gel 0.3% was superior to adapalene gel 0.1% and vehicle in the treatment of moderate to moderately severe acne while retaining a similar safety and tolerability profile to adapalene 0.1% gel.

Acne Vulgaris↗
PubMed2004

A computational approach for ordering signal transduction pathway components from genomics and proteomics Data.

BACKGROUND: Signal transduction is one of the most important biological processes by which cells convert an external signal into a response. Novel computational approaches to mapping proteins onto signaling pathways are needed to fully take advantage of the rapid accumulation of genomic and proteomics information. However, despite their importance, research on signaling pathways reconstruction utilizing large-scale genomics and proteomics information has been limited. RESULTS: We have developed an approach for predicting the order of signaling pathway components, assuming all the components on the pathways are known. Our method is built on a score function that integrates protein-protein interaction data and microarray gene expression data. Compared to the individual datasets, either protein interactions or gene transcript abundance measurements, the integrated approach leads to better identification of the order of the pathway components. CONCLUSIONS: As demonstrated in our study on the yeast MAPK signaling pathways, the integration analysis of high-throughput genomics and proteomics data can be a powerful means to infer the order of pathway components, enabling the transformation from molecular data into knowledge of cellular mechanisms.

Computational Biology↗
PubMed2004

Kinase peptide specificity: improved determination and relevance to protein phosphorylation.

Specificity of phosphorylation is critical to signal transduction. Recent emphasis on colocalization of substrate and kinase has eclipsed emphasis on peptide specificity, i.e., kinase preference for particular amino acids surrounding the phosphorylation site. We describe an approach to determining peptide specificity by using positional scanning of biotinylated oriented peptide libraries and insights emerging from those determinations. We accurately determine preference (or disfavor) for residues at a given substrate position (such as P+2) by comparison of in vitro phosphorylation of peptide libraries differing by a single residue at that position. By analysis of all positions near the phosphorylation site, position-specific scoring matrices are generated and used both to understand the basis of specificity and to predict phosphorylation. PKC-delta and -zeta predictions have been validated rigorously by comparisons with measured phosphorylation. The results demonstrate specificity and sensitivity (80-90%) much better than the previous predictive method. These predictions can be accessed at http://mpr.nci.nih.gov. The accuracy of the specificity determination allows identification of an important difference in peptide specificity between these closely related kinases; Ile/Leu at the P-1 position is disfavored by PKC-zeta but not PKC-delta. Our findings and visual representation of peptide specificity highlight the importance of disfavored residues. Finally, analysis of 124 experimentally determined PKC sites from the literature demonstrates a very strong role of peptide specificity in many of those sites. Thus, position-specific scoring matrices generated by this method provide a foundation for quantitative analyses of kinase specificity and improved predictions of previously determined physiologically relevant phosphorylation sites.

Cyclic AMP-Dependent Protein Kinases↗
PubMed2004

Obesity induced by a high-fat diet downregulates apolipoprotein A-IV gene expression in rat hypothalamus.

Apolipoprotein A-IV (apo A-IV) is an anorectic protein produced in the intestine and brain that has been proposed as a satiety signal. To determine whether diet-induced obesity alters apo A-IV gene expression in the intestine and hypothalamus, rats were fed a high-fat (HF), low-fat (LF), or standard chow (CHOW) diet for 2, 4, 6, 8, or 10 wk. Rats fed the HF diet had significantly greater body weights than rats given the LF and CHOW diets. Intestinal and plasma apo A-IV levels were comparable across dietary groups and time. LF and CHOW rats had comparable hypothalamic apo A-IV mRNA across the course of the experiment. However, HF rats had a slow and progressive diminution in hypothalamic apo A-IV mRNA over time that became significantly lower than that of LF or CHOW rats by 10 wk. Intragastric infusion of lipid emulsion to animals that were fasted overnight significantly stimulated hypothalamic apo A-IV mRNA in LF and CHOW rats but had no effect in HF rats. These results demonstrate that chronic consumption of a HF diet significantly reduces apo A-IV mRNA levels and the response of apo A-IV gene expression to dietary lipids in the hypothalamus. This raises the possibility that dysregulation of hypothalamic apo A-IV could contribute to diet-induced obesity.

Adaptation, Physiological↗
PubMed2004

Diurnal rhythm of apolipoprotein A-IV in rat hypothalamus and its relation to food intake and corticosterone.

Apolipoprotein A-IV (apo A-IV) is a satiety protein synthesized in the small intestine and hypothalamus. To further understand the roles of central apo A-IV in the management of daily food intake, we have examined the diurnal patterns of hypothalamic apo A-IV gene and protein expression in freely feeding and food-restricted (food provided 4 h daily between 1000 h and 1400 h) rats. In freely feeding rats, the hypothalamic apo A-IV mRNA and protein levels fluctuated, with high levels during the light phase, peaking at 0900 h (3 h after lights on), and low levels during the dark phase, with a nadir at 2100 h (3 h after lights off). The daily patterns of the fluctuation, however, were altered in food-restricted rats, which had a marked decrease in hypothalamic apo A-IV mRNA and protein levels during the 4 h-feeding period of the light phase. Although corticosterone (CORT) secretion temporally coincided with the decreasing phase of apo A-IV in the hypothalamus, depletion of CORT by adrenalectomy significantly decreased, rather than increased, hypothalamic apo A-IV mRNA and protein levels. These results indicate that the diurnal expression of hypothalamic apo A-IV is regulated by factors other than the circulating CORT, for example, the reduced food intake and body weight in adrenalectomized animals. The fact that hypothalamic apo A-IV level and food intake were inversely related during the normal diurnal cycle as well as in the period of restricted feeding suggests that hypothalamic apo A-IV is involved in the regulation of daily food intake.

Adrenalectomy↗
PubMed2004

Suppression of 6A8 alpha-mannosidase gene expression reduced the potentiality of growth and metastasis of human nasopharyngeal carcinoma.

Suppression of alpha-mannosidases by chemicals has been shown to reduce the potentiality of growth and metastasis of various tumors. In our study, the effect of 6A8 alpha-mannosidase (MAN 6A8), recently discovered in our laboratory, on malignant behaviors of tumor cells was examined. Since the suppressive effect of chemicals on alpha-mannosidase is not specific, antisense technique was used to specifically inhibit expression of the MAN 6A8 in human nasopharyngeal carcinoma cells, CNE-2L2. Two cell clones, AS1 and AS2, with pronounced suppression of MAN 6A8 expression were developed. Wild-type (W), mock-transduced (M) and irrelevant DNA-transduced (IR) CNE-2L2 cells with normal expression of the enzyme were used as controls. Malignant behaviors of the cells were examined. Significant inhibition of growth of AS cells in vitro measured by MTT assay, colony formation and anchorage-independent colony formation was found. Pronounced inhibition of formation of tumors from AS cells inoculated into nude mice and metastasis was also observed. W, M and IR cells cultured in plate wells appeared dispersed with a fibroblastic or epithelial morphology, whereas AS cells were in compact sheets with an epithelioid organization. Since E-cadherin is the key factor in homophilic adhesion of epithelial cells, its expression on the surface of CNE-2L2 cells was determined. E-cadherin expression on AS cells was enhanced, whereas it was markedly diminished on W, M and IR cells. In addition, lamellipodia, which play an important role in cell spreading and mobility, almost disappeared on AS cells. The results demonstrate a significant suppressive effect of reduced expression of MAN 6A8 on malignant behaviors of CNE-2L2 cells.

Animals↗
PubMed2004

Anticonvulsive effect of agmatine in mice.

The present study was designed to examine the effect of agmatine, the decarboxylated product of L-arginine by L-arginine decarboxylase, on convulsion in the mouse maximal electroshock (MES) test and mouse glutamate-induced convulsant test. MES convulsion and glutamate convulsion were respectively induced by an electrical stimulation (110 V, 0.3 s, 8 Hz) and by intracerebroventricular injection of glutamate (0.5 M, pH 7.4, 5microl). The results were expressed as the tonic and clonic time of convulsion in MES or percentage of mice with tonic hind-limb extension in glutamate-induced convulsant assay. Agmatine given intracerebroventricularly (2-16 mg/kg) or subcutaneously (10-160 mg/kg) significantly shortened the tonic and clonic times of convulsion in a dose-dependent manner in the mouse MES test. Glutamate (0.5 M, 5microl icv per mouse) induced an obvious convulsive response indicated by tonic hind-limb extension in mice, and agmatine (2-16 mg/kg icv) decreased the rate of mice with tonic hind-limb extension like NMDA receptor antagonist MK-801. The anticonvulsive effect of agmatine (80 mg/kg sc) on both the tonic and clonic times of convulsion lasted for more than 4 h after administration in the mouse MES test, which was twice that of barbital. Taken together, the results implicate that agmatine has obvious anticonvulsive effects, and its possible mechanism might be related to the antagonism of the function of NMDA receptors.

Agmatine↗
PubMed2003

Down-regulation of transcription of the proapoptotic gene BNip3 in cultured astrocytes by murine coronavirus infection.

Murine coronavirus mouse hepatitis virus (MHV) causes encephalitis and demyelination in the central nervous system of susceptible rodents. Astrocytes are the major target for MHV persistence. However, the mechanisms by which astrocytes survive MHV infection and permit viral persistence are not known. Here we performed DNA microarray analysis on differential gene expression in astrocyte DBT cells by MHV infection and found that the mRNA of the proapoptotic gene BNip3 was significantly decreased following MHV infection. This finding was further confirmed by quantitative reverse transcription-polymerase chain reaction, Western blot analysis, and BNip3-promoter-luciferase reporter system. Interestingly, infection with live and ultraviolet light-inactivated viruses equally repressed BNip3 expression, indicating that the down-regulation of BNip3 expression does not require virus replication and is mediated during cell entry. Furthermore, treatment of cells with chloroquine, which blocks the acidification of endosomes, significantly inhibited the repression of the BNip3 promoter activity induced by the acidic pH-dependent MHV mutant OBLV60, which enters cells via endocytosis, indicating that the down-regulation of BNip3 expression is mediated by fusion between viral envelope and cell membranes during entry. Deletion analysis showed that the sequence between nucleotides 262 and 550 of the 588-base-pair BNip3 promoter is necessary and sufficient for driving the BNip3 expression and that it contains signals that are responsible for MHV-induced down-regulation of BNip3 expression in DBT cells. These results may provide insights into the mechanisms by which MHV evades host antiviral defense and promotes cell survival, thereby allowing its persistence in the host astrocytes.

Animals↗
PubMed2003

Millions of years of evolution preserved: a comprehensive catalog of the processed pseudogenes in the human genome.

Processed pseudogenes were created by reverse-transcription of mRNAs; they provide snapshots of ancient genes existing millions of years ago in the genome. To find them in the present-day human, we developed a pipeline using features such as intron-absence, frame-disruption, polyadenylation, and truncation. This has enabled us to identify in recent genome drafts approximately 8000 processed pseudogenes (distributed from http://pseudogene.org). Overall, processed pseudogenes are very similar to their closest corresponding human gene, being 94% complete in coding regions, with sequence similarity of 75% for amino acids and 86% for nucleotides. Their chromosomal distribution appears random and dispersed, with the numbers on chromosomes proportional to length, suggesting sustained "bombardment" over evolution. However, it does vary with GC-content: Processed pseudogenes occur mostly in intermediate GC-content regions. This is similar to Alus but contrasts with functional genes and L1-repeats. Pseudogenes, moreover, have age profiles similar to Alus. The number of pseudogenes associated with a given gene follows a power-law relationship, with a few genes giving rise to many pseudogenes and most giving rise to few. The prevalence of processed pseudogenes agrees well with germ-line gene expression. Highly expressed ribosomal proteins account for approximately 20% of the total. Other notables include cyclophilin-A, keratin, GAPDH, and cytochrome c.

Animals↗
PubMed2003

Induction of caspase-dependent apoptosis in cultured rat oligodendrocytes by murine coronavirus is mediated during cell entry and does not require virus replication.

Murine coronavirus mouse hepatitis virus (MHV) causes demyelination of the central nervous system (CNS) in rats and mice. Apoptotic oligodendrocytes have been detected in the vicinity of the CNS demyelinating lesions in these animals. However, whether MHV can directly induce oligodendrocyte apoptosis has not been documented. Here, we established a rat oligodendrocyte culture that is morphologically and phenotypically indistinguishable from the primary rat oligodendrocytes. Using this culture, we showed that mature rat oligodendrocytes were permissive to MHV infection but did not support productive virus replication. Significantly, oligodendrocytes infected with both live and ultraviolet light-inactivated viruses underwent apoptosis to a similar extent, which was readily detectable at 24 h postinfection as revealed by apoptotic bodies and DNA fragmentation, indicating that MHV-induced apoptosis is mediated during the early stages of the virus life cycle and does not require virus replication. Prior treatment of cells with the lysosomotropic agents NH(4)Cl and chloroquine as well as the vacuolar proton pump-ATPase inhibitor bafilomycin A1, all of which block the acidification of the endosome, prevented oligodendrocytes from succumbing to apoptosis induced by MHV mutant OBLV60, which enters cells via endocytosis, indicating that fusion between the viral envelope and cell membranes triggers the apoptotic cascade. Treatment with the pan-caspase inhibitor Z-VAD-fmk blocked MHV-induced apoptosis, suggesting an involvement of the caspase-dependent pathway. Our results, thus, for the first time provide unequivocal evidence that infection of oligodendrocytes with MHV directly results in apoptosis. This finding provides an explanation for the destruction of oligodendrocytes and the damage of myelin sheath in MHV-infected CNS and suggests that oligodendrocyte apoptosis may be one of the underlying mechanisms for the pathogenesis of MHV-induced demyelinating diseases in animals.

Animals↗
PubMed2003

[Inhibition of ER alpha-mannosidase expression causes reduction and shortening of microvilli on rat liver epithelial cell WB-F344].

OBJECTIVE: To study the effect of N-glycosylation on the modification of microvilli on the surface of rat liver epithelial cell WB-F344 and the growth of the cells in culture. METHODS: Recombinant adeno-associated virus (rAAV) expression vector pAGX (+) containing an antisense or a sense fragment of 6A8 cDNA encoding a human alpha-mannosidase was constructed. The recombinant vectors or the mock were transfected into WB-F344 cells by means of lipofectAmine. The transfected cells were selected in G418 medium and cloned by means of limiting dilution. Integration of the transfected DNA into host DNA was detected by neo PCR. Rat liver ER alpha-mannosidase activity in cell supernatant was measured by using P-nitrophenyl-alpha-D-mannopyranoside as a substrate. Microvilli on cell surface were observed upon a scan electron microscope. The growth curves of the cells in culture were drawn. RESULTS: The cell clones transfected with antisense 6A8 showed reduction of ER alpha-mannosidase activity with various degrees. Clone AS1 and AS2 cell showed a pronounced reduction of the enzymatic activity. In the study on AS1 cells, Con A binding to the cells was found to be enhanced, cell growth in culture became slow from day 5. The microvilli on the cells were reduced and blunted. CONCLUSIONS: Transfection with antisense 6A8 resulted in reduction and blunting of microvilli on the surface of growing WB-F344 cells, which might be related to N-glycosylation modification.

Animals↗
PubMed2003

[Inhibition of 6A8 alpha-manosidase expression induces decrease of adhesion to laminin and reduction of lamellipodia of human nasopharyngeal carcinoma cell CNE-2L2].

OBJECTIVE: To investigate the inhibitory effect of 6A8 alpha-manosidase expression on the adhesiveness of CNE-2L2 cells to laminin and the lamellipodia on cell surface. METHODS: 6A8 alpha-manosidase expression was detected by Western blotting. For assaying the adhesion of cells to laminin, cells were incubated in laminin-coated plate at 37 degrees C for 1 h, the adhered cells were stained with crystal purple dissolved in 0.1 mol/L Sodium Citrate/50% ethanol. Absorbance 540 nm was measured. Adhesion rate (R) was calculated according to formula R = AT/A100 x 100%. Here A100 represents 100% adhesion. lamellipodia on cell surface was observed upon a scanning electron microscopy. RESULTS: The adhesion rate of two clones (AS1 and AS2) with inhibition of 6A8 alpha-manosidase expression to laminin was 0.447 +/- 0.096 and 0.533 +/- 0.065 respectively. The adhesion rate of three controls with normal expression of 6A8 alpha-manosidase to laminin was 0.78 +/- 0.035, 0.7 +/- 0.05 and 0.80 +/- 0.04 respectively. The difference was significant (P < 0.01). CNE-2L2 cells with normal expression of 6A8 alpha-manosidase was rich in lamellipodia on their surface. Lamellipodia nearly disappeared on the cells with inhibition of 6A8 alpha-manosidase expression. CONCLUSIONS: Inhibition of 6A8 alpha-manosidase expression results in decrease of adhesion to laminin and reduction of lamellipodia of human nasopharyngeal carcinoma cell CNE-2L2.

Cell Adhesion↗
PubMed2003

Antimalarial effect of agmatine on Plasmodium berghei K173 strain.

AIM: To study the antimalarial effect of agmatine (Agm) on chloroquine-susceptible Plasmodium berghei K173 strain (S strain) and the P berghei K173 resistant strain (R strain). METHODS: The antimalarial effects of Agm on P berghei K173 S strain and R strain were evaluated by Peters 4-d suppression test in mice. RESULTS: Agm (12.5-200 mg/kg, ig, daily) decreased the parasitemia for both P berghei K173 S strain (IC(50)=139 mg/kg) and R strain (IC(50)=126 mg/kg) in mice. Subcutaneous injection (sc) of Agm (5-40 mg/kg, tid) showed relatively stronger antimalarial effect than intragastric gavage (IC(50)=30 mg/kg ) in P berghei K173 S strain. Spermidine antagonized the antimalarial effect of Agm for P berghei K173 S strain and R strain. Agm did not reverse the chloroquine resistance of P berghei K173 S strain. dl-alpha-Difluoromethylornithine (DFMO, sc) decreased the parasitemia of P Berghei K173 S strain and this effect was antagonized by spermidine. CONCLUSION: Agm has an antimalarial effect and the mechanism is related to its inhibition of polyamine synthesis.

Agmatine↗